High-intensity, persistent thermochromic compositions and objects, and methods for creating the same

ABSTRACT

Disclosed are thermochromic formulations, comprising an effective amount of thermochromic materials, which exhibit high luminous intensity and persistence. Also disclosed are thermochromic objects formed by applying at least one thermochromic layer, formed from thermochromic formulations, to preformed articles. Further disclosed are methods for creating thermochromic objects.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 60/637,535, filed Dec. 20, 2004 (Attorney Docket No.7044531001), titled, “Layered Envirochromic Materials, Applications andMethods of Preparation Thereof,” which is incorporated by referenceherein for all purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to thermochromic compositionscomprising an effective amount of thermochromic materials formulated toyield change in color of high intensity. The present invention is alsodirected to thermochromic objects comprising at least one envirochromiclayer, wherein said envirochromic layer comprises at least onethermochromic composition. Thermochromic objects may also additionallycomprise at least one reflective layer, at least one colorant layer,and/or at least one protective layer. Such protective layers comprisephotoluminescent fluorescent materials to retard photolytic degradation.The present invention is further directed to methods for creatingthermochromic objects, said methods comprising the steps of obtaining apreformed article and applying thereto at least one envirochromic layerconstructed by applying said thermochromic materials, and wherein onemay additionally apply to said preformed article said reflective layer,and/or said colorant layer, and/or said protective layer.

2. Description of the Related Art

Modern consumers are looking for added information and features from theproducts that they purchase. Desirable products are those that meetspecific needs and/or provide added benefits to the consumer. Thesespecific needs or added benefits may be safety controls or indicators,environmental information indicators, shelf life indicators,authentication and tamper indicators, fashion accessory benefits, and/orfun & entertainment benefits. These added benefits can be created, orindicators provided, by triggering a color change as a response to theproduct's environment.

Envirochromic materials are those whose visible color changes due toemission, absorption reflection, or scattering of electromagneticradiation. Such emission, absorption, reflection, or scattering ofelectromagnetic radiation results from a change in the material'senvironment. These changes, or “triggers,” include change intemperature, change in electromagnetic radiation, change in chemicalenvironment, an electrical stimulus, etc.

Color change can occur by changes in electromagnetic radiation,reflection, absorption or scattering. Thus, for example, photochromismsignifies color change triggered by electromagnetic radiation;thermochromism signifies color change triggered by changes intemperature; electrochromism signifies changes in color occurring due togain or loss of electrons; solvatochromism signifies color changeresulting from changes in solvent polarity; halochromism signifies colorchange caused by a change in pH; ionochromism signifies color changecaused by ions; tribochromism caused by changes in mechanical friction;and piezochromism signifies changes caused by mechanical pressure.

Color change can also result from luminescent emissions. Hence, whendealing with color changes resulting from emissions, we will use“luminescence” or “luminescent” to signify the color change.

This invention deals with color changes not only resulting fromtemperature-triggered color changes as a consequence of changes inabsorption reflection and/or scattering of electromagnetic radiation,hereinafter referred to as “thermochromic,” but also from luminescentemissions which will be designated as “luminescent” or “luminescence.”

Thermochromism can be triggered, in general, by inorganic compounds,organic compounds, polymers, and sol-gels.

Inorganic Compound Thermochromism

Many metals and inorganic compounds are known to exhibit thermochromicbehavior either as solids or in solution. It has been suggested thatsuch thermochromic behavior arises from phase transition, change inligand geometry, equilibria between different molecular structures, andchange in the number of solvent molecules in the coordination sphere.

Certain metal complex crystals comprising double salts of a transitionmetal such as cobalt, nickel, or manganese, and an aminic amide, such ashexamethylenetetramine, exhibit thermochromism. See, e.g., U.S. Pat. No.4,717,710. These double salts discolor on releasing water when heatedand resume the original color on absorption of moisture when cooled. Id.

However, in these metal complex crystals, the thermochromic temperaturerange is substantially from 50° C. to about 300° C. More specifically,the number of substances undergoing thermochromism at temperatures below100° C. is limited to 2 or 3. For instance, in the case of Ag₂ HgI₄, thethermochromism is from yellow to orange occurs at 50° C., and in thecase of Cu₂ HgI₄ thermochromism from red to brown is brought about at70° C. See, e.g., U.S. Pat. No. 4,028,118. Of course, the kind of colorcannot be optionally chosen and the difference between colors before andafter thermochromism is small. Moreover, since these metal complexcrystals are not light-transmitting, it is not possible to use them asoptical switches to hide/reveal an indicia, pattern or color in thelayer below. Id.

These materials have heretofore been used as thermochromic materials buttheir applications are limited.

Organic Compound Thermochromism

The mechanism responsible for thermochromism varies with molecularstructure. It may be due to equilibrium between two molecular species,acid-base, keto-enol, lactim-lactam, or between stereoisomers or betweencrystal structures.

Thermochromic liquid crystals show different colors at differenttemperature because of selective reflection of specific wavelength ofelectromagnetic radiation from their structure. In an appropriatetemperature range intermediate between a low-temperature crystallinephase and a high-temperature isotropic liquid phase, these materialsform a cholesteric liquid crystal. In a cholesteric liquid crystal,changes in temperature result in thermal expansion, which leads to achange in layer spacing and hence pitch, which results in a change inthe wavelength of reflected light and hence a color change is observedwith varying temperature. We present below an example of such a materialthat is used in the manufacture of a thermochromic printing ink.

Thermochromic substances further include cholesteric liquid crystals andmixtures of cholesteric liquid crystals and nematic liquid crystals, butthese substances also find greatly limited use because they are low incolor density, have no selectivity in color and in color changetemperature and are very expensive. See, e.g., U.S. Pat. No. 4,717,710.

Liquid crystals generally exhibit thermochromism at temperatures rangingfrom −10° C. to +200° C. However, the number of liquid crystalsundergoing thermochromism at a temperature not exceeding 0° C. is verylimited, namely 1 or 2. The color or thermochromism causing temperaturecannot freely be chosen but is determined by the properties of theliquid crystals per se. These compounds are also chemically verysensitive; their properties are readily degraded upon contact with othersubstances.

Thermochromic liquid crystal materials tend to be expensive andgenerally exhibit low color density. Hence, their use is not widespread,occurring in specialized situations

Thermochromism arising from variations in stereoisomers in mostlyassociated with “overcrowded” ethylenes, such as Bianthrone,Dixanthylene, and Xanthylidenanthrone. These compounds are characterizedby at least one ethylene group, a number of aromatic rings, and ahetero-atom, usually nitrogen or oxygen. The ethylene bond places arestriction on the molecular orientations possible, thereby increasingthe energy barrier between different streoisomeric configurations. Asthe temperature is increased, the molecule “switches” between differentstereoisomers, this change being accompanied by a variation in color.For a majority of compounds that exhibit this behavior, thermochromismoccurs at temperatures in excess of 150° C. For example, bianthrone iscolorless when solid, but forms green droplets above its melting point.

The molecular rearrangement of an organic compound that arises fromtautomerization can lead to an increase in the conjugation of themolecule, and consequently the formation of a new chromophore. Suchmolecular rearrangement can be effected by a change in temperature or byalteration of the polarity of the solvent and/or the pH of the system.Examples are, acid-base, keto-enol, and Lactim-Lactam equilibrium.

Although fundamentally the chromism is pH-dependent, thetemperature-dependence of the acid-base equilibrium means that pHsensitivity can result in thermochromic behavior. We present below onesuch example of crystal violet lactone.

It should be noted that crystal violet Lactone does not exhibitthermochromism below a pH of 4. That is, even upon heating the ringopening does not occur and the colored form predominates. On the otherhand, at higher pHs and upon heating equilibrium will shift to the leftand the dye will become colorless.

The mechanism described above has been commercialized the most, andthere is a wide variety of thermochromic materials available.Specifically, the commonly-employed thermochromic system is one whereinmolecular rearrangement occurs by a reaction between an electrondonating compound referred to as a color former and an electronaccepting compound referred to as a developer.

These compositions have the following advantages: (1) Thermochromicmaterials can be formulated for various colors; (2) The thermochromicmaterials gives a high color density; and (3) Depending on the kind ofsolvent, the color change temperature can be set over a wide range oflow to high temperatures.

To summarize, thermochromic materials of this type generally comprise anelectron donating compound, an electron accepting compound, and organicsolvents to control the temperature and sensitivity of the thermochromiceffect. It can be appreciated that since thermochromism is anequilibrium reaction, the two component systems can be very sensitive totheir environment and hence are generally encapsulated to make themamenable to deployment in different formulations. See, e.g., U.S. Pat.Nos. 4,028,118; 4,421,560; 4,425,161; and 4,717,770.

It can be seen that there are a wide variety of thermochromic materialsbut which are generally very sensitive to their physical and chemicalenvironment, which can comprise solvents, polymeric resin binders,stabilizing additives, pigments, dyes etc., which if not controlled, canquickly result in a degradation of the degree of color change, or evencomplete loss of thermochromic performance. Even for the case whenthermochromic materials are encapsulated, to enable greater formulationflexibility for application to various substrates deploying a variety oftechniques, the materials are still quite sensitive to their physicaland chemical environment since the encapsulant is still porous. For theuse of these materials as envirochromic materials that serve asindicators, as described above, it is essential for the color change tobe perceived as vibrant.

Even if the chemical environment does not impact the thermochromicmaterials, it can impact the capsule material. For example, the solventcan swell the polymeric capsule wall, thereby making it a scatterer ofelectromagnetic radiation. In cases where thermochromic materials areused as an optical switch, the changed color state will appear whiteand/or hazy instead of clear.

For single layer constructions, even if the thermochromic materialenvironment is carefully selected so that the thermochromic performanceis not degraded, the solvents used can leach harmful materials from thesubstrate over which these materials are applied.

Even though progress has been made over the years in expanding thecolors and temperature ranges available, since thermochromic materialshave generally been deployed as single layer applications, the colorgamut is still fairly limited. With single layer embodiments, pigmentsare added to colorants in order to expand the range of colors that canbe achieved. However, when color results from absorption ofelectromagnetic radiation, creating colors with combinations ofthermochromic materials of limited color range, and pigment colorants,is still quite restrictive in the range of bright colors that can beachieved.

Additionally, for outdoor usage, thermochromic materials are not onlysubject to photolytic degradation but by virtue of their sensitivity,need to be protected from mechanical forces such as abrasion, etc.

Specific thermochromic materials and mixtures of thermochromic materialswill need to be adapted to provide the requisite color change.Thermochromic materials usually exist as solids or liquid crystals in acarrier medium.

When thermochromic materials are used as an optical switch, thetheromochromic material needs to be formulated with clear resins andsolvents that do not interact. Vibrant color layer formulations usingsolvents that do not leach are also desired.

Outdoor usage of thermochromic objects also necessitates good adhesionto substrates and mechanical toughness such as scratch resistance, etc.,specific requirements being dictated by the application.

Accordingly, in view of the above, there is a need for thermochromicmaterials and thermochromic objects created from such materials that canserve as safety indicators, fashion indicators, or create fun andentertainment by triggering temperature-activated color changes that arevibrant and impactful. The thermochromic objects can also be created ina variety of standard and emissive colors, also with high intensity. Thethermochromic objects are also created to minimize photolyticdegradation, do not degrade with moisture, and are mechanically robust,particularly in outdoor applications.

BRIEF SUMMARY OF THE INVENTION

It has now been found that formulations comprising an effective amountof thermochromic materials, at least one liquid carrier medium, at leastone polymeric resin, and at least one formulation stabilizing additive,wherein said thermochromic materials are uniformly distributed withinsaid formulation provide thermochromic formulations with high intensityand persistence.

Accordingly, in one of its formulation aspects, the present invention isdirected to a thermochromic formulation comprising an effective amountof thermochromic materials, at least one liquid carrier medium, at leastone polymeric resin, and at least one formulation stabilizing additive,wherein said thermochromic materials are uniformly distributed withinsaid formulation.

In another formulation embodiment, the present invention is directed toa thermochromic formulation comprising an effective amount ofthermochromic materials, at least one liquid carrier medium, at leastone polymeric resin, and at least one formulation stabilizing additive,wherein said thermochromic materials are uniformly distributed withinsaid formulation and wherein the theromchromic formulation has an FT ofat least 90%.

In one of its object embodiments, the present invention is directed to athermochromic object comprising a performed article and at least onethermochromic layer, wherein the thermochromic layer results from theforegoing thermochromic formulations.

In yet another object embodiment, the present invention is directed to athermochromic object comprising a preformed article, at least onethermochromic layer, and at least one reflective layer, wherein thethermochromic layer results from the foregoing thermochromicformulations, wherein the reflective layer results from a reflectiveformulation, wherein the reflective layer is proximal to said preformedarticle, and wherein said thermochromic layer is distal to saidpreformed article.

In yet another object embodiment, the present invention is directed to athermochromic object comprising a preformed article, at least onethermochromic layer, at least one reflective layer, and at least oneprotective layer, wherein the thermochromic layer results from theforegoing thermochromic formulations, wherein the reflective layerresults from a reflective formulation, wherein said protective layerresults from a protective formulation, wherein the reflective layer isproximal to said preformed article, and wherein said protective layer isdistal to said preformed article, and wherein said thermochromic layeris between said reflective layer and said protective layer.

In yet another object embodiment, the present invention is directed to athermochromic object comprising a preformed article, at least onethermochromic layer, and at least one protective layer, wherein thethermochromic layer results from the foregoing thermochromicformulations, wherein the protective layer results from a protectiveformulation, wherein the thermochromic layer is proximal to saidpreformed article, and wherein said protective layer is distal to saidpreformed article.

In one of its method aspects, the present invention is directed to amethod for creating a thermochromic object, said method comprising thesteps of obtaining a preformed article and applying to said preformedarticle at least one thermochromic layer, wherein said thermochromiclayer results from the foregoing thermochromic formulations.

In yet another method embodiment, the present invention is directed to amethod for creating a thermochromic object, said method comprising thesteps of obtaining a preformed article, applying to said preformedarticle at least one thermochromic layer, and applying to said preformedarticle at least one reflective layer, wherein the thermochromic layerresults from the foregoing thermochromic formulations, wherein thereflective layer results from a reflective formulation, wherein thereflective layer is proximal to said preformed article, and wherein saidthermochromic layer is distal to said preformed article.

In yet another method embodiment, the present invention is directed to amethod for creating a thermochromic object, said method comprising thesteps of obtaining a preformed article, applying to said preformedarticle at least one thermochromic layer, applying to said preformedarticle at least one reflective layer, and applying to said preformedarticle at least one protective layer, wherein the thermochromic layerresults from the foregoing thermochromic formulations, wherein thereflective layer results from a reflective formulation, wherein saidprotective layer results from a protective formulation, wherein thereflective layer is proximal to said preformed article, and wherein saidprotective layer is distal to said preformed article, and wherein saidthermochromic layer is between said reflective layer and said protectivelayer.

In yet another object embodiment, the present invention is directed to amethod for creating a thermochromic object, said method comprising thesteps of obtaining a preformed article, applying to said preformedarticle at least one thermochromic layer, and applying to said preformedarticle at least one protective layer, wherein the thermochromic layerresults from the foregoing thermochromic formulations, wherein theprotective layer results from a protective formulation, wherein thethermochromic layer is proximal to said preformed article, and whereinsaid protective layer is distal to said preformed article.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates how absorption of ultraviolet radiation by a moleculeexcites it from a vibrational level in the electronic ground state toone of the many vibrational levels in the electronic excited state, suchas singlet states and triplet states.

FIG. 2 is a Jablonski Diagram illustrating processes that occur betweenthe absorption and emission of electromagnetic radiation.

FIG. 3 is a stylized depiction of an embodiment of the invention wherebya thermochromic object is created using a preformed article 1 with athermochromic layer 2 applied thereto.

FIG. 4 is a stylized depiction of an embodiment of the invention wherebya thermochromic object is created using a preformed article 1 with areflective layer 3 and a thermochromic layer 2 applied thereto.

FIG. 5 is a stylized depiction of an embodiment of the invention wherebya thermochromic object is created using a preformed article 1 with atheromchromic layer 2 and a protective layer 4 applied thereto.

FIG. 6 is a stylized depiction of an embodiment of the invention wherebya thermochromic object is created using a preformed article 1 with areflective layer 3, a thermochromic layer 2, and a protective layer 4applied thereto.

FIG. 7 is a stylized depiction of an embodiment of the invention wherebytransfer technology is used to obtain the thermochromic object.

FIG. 8 is a stylized depiction of an embodiment of the invention wherebya thermochromic object is created using a preformed article 1 with areflective layer 3, a first thermochromic layer 2, a secondthermochromic layer 5, a first protective layer 4, and second protectivelayer 6 applied thereto.

FIG. 9 is a stylized depiction of an embodiment of the invention wherebya thermochromic object is created using a preformed article 1 with areflective layer 3, a first thermochromic layer 2, a secondthermochromic layer 5, and a first protective layer 4 applied thereto.

FIG. 10 is a stylized depiction of an embodiment of the inventionwhereby a thermochromic object is created using a preformed article 1with a reflective layer 3, a first thermochromic layer 2, a firstprotective layer 4, and second protective layer 6 applied thereto.

DETAILED DESCRIPTION OF THE INVENTION

As noted above, the present invention generally relates to thermochromicformulations, thermochromic objects comprising preformed articles ontowhich said thermochromic formulations have been applied, and to methodsfor creating said thermochromic objects.

Prior to discussing the invention in detail, the following terms willfirst be defined.

The term “luminescence” is defined as the emission of electromagneticradiation from any substance. Luminescence occurs from electronicallyexcited states. As seen in FIG. 1, absorption of ultraviolet radiationby a molecule excites it from a vibrational level in the electronicground state to one of the many vibrational levels in the electronicexcited states. The electronic states of most organic molecules can bedivided into singlet states and triplet states.

As used herein, “singlet state” refers to when all electrons in themolecule are spin-paired. As used herein, “triplet state” refers to whenone set of electron spins is unpaired. The excited state is usually thefirst excited state. A molecule in a high vibrational level of theexcited state will quickly fall to the lowest vibrational level of thisstate by losing energy to other molecules through collision. Themolecule will also partition the excess energy to other possible modesof vibration and rotation.

“Luminescent materials” are those which emit electromagnetic radiation.Characterizing luminescent materials requires consideration of: (1) theexcitation source, (2) the nature of the emission, and (3) whether ornot additional stimulation is required to cause emission.

With regard to the excitation source, luminescent materials excited byelectromagnetic radiation are referred to herein as “photoluminescent.”Luminescent materials excited by electrical energy are referred toherein as “electroluminescent.” Luminescent materials excited by achemical reaction are referred to herein as “chemiluminescent.”

With regard to the nature of the emission, this may be eitherfluorescence or phosphorescence. A “fluorescent” material storeselectromagnetic radiation and releases it rapidly, in about 10⁻¹²seconds or less. Contrarily, a “phosphorescent” material storeselectromagnetic radiation and releases it gradually, in about 10⁻⁸seconds or more.

Processes that occur between the absorption and emission ofelectromagnetic radiation are usually illustrated using a JablonskiDiagram, such as the one found in FIG. 2. Ground, first, and secondelectronic states are depicted in FIG. 2 by S₀, S₁, and S₂,respectively. At each electronic energy level, the fluorophores canexist in a number of vibrational energy levels, denoted by 0, 1, 2, etc.Transitions between states are depicted in FIG. 2 as vertical lines toillustrate the instantaneous nature of electromagnetic radiationabsorption.

“Fluorescence” occurs when a molecule returns, by emission of a photon,from the excited singlet state to the electronic ground state. If thephoton emission occurs between states of the same spin state, that is,from S₁ to S₀, it is characterized as fluorescence.

“Phosphorescence” occurs when a molecule goes from the ground state to ametastable state such as T1, a triplet state, and then the metastablestate slowly decays back to the ground state S₀, via photon emission.Hence, if the spin states between initial and final energy levels aredifferent, that is emission occurs between T₁ to S₀, it is characterizedas phosphorescence.

The term “thermochromic” is defined as characterizing a change inabsorption, reflection, and/or scattering of electromagnetic radiationwith a change in temperature to cause a change in the perceived color,wherein the color change may be from colorless to colored, or colored tocolorless, or from one color to another.

“Thermochromic materials” are defined to mean materials that undergo achange in absorption, reflection, and/or scattering of electromagneticradiation with a change in temperature to cause a change in theperceived color of the materials wherein the color change may be fromcolorless to colored, or colored to colorless, or from one color toanother.

“Thermochromic objects” are defined to mean objects that undergo achange in absorption, reflection, and/or scattering with a change intemperature to cause a change in the perceived color of the objectwherein the color change may be from colorless to colored, or colored tocolorless or from one color to another.

“Negative thermochromism” is defined to describe a temperature-triggeredcolor change resulting from a change in absorption, reflection, and/orscattering wherein the color change is from a colored state to acolorless state.

“Positive thermochromism” is defined to describe a temperature-triggeredcolor change resulting from a change in absorption, reflection, and/orscattering of electromagnetic radiation wherein the color change is froma colorless to colored state.

“Neutral thermochromism” is defined to describe a temperature-triggeredcolor change resulting from a change in absorption, reflection, and/orscattering of electromagnetic radiation wherein the color change is fromone color to another color.

“Liquid carrier medium” is a liquid that acts as a carrier for materialsdistributed in a solid state and/or dissolved therein.

As used herein, a “formulation” is a liquid carrier medium, as definedabove, comprising at least one material either dissolved and/ordistributed in a solid state within said liquid carrier medium.

A “dispersion” is a formulation, as defined above, wherein said materialis a solid distributed in the liquid carrier medium.

A “thermochromic formulation” is a formulation, as defined above, whichadditionally comprises thermochromic materials as defined above.

As used herein, a “thermochromic layer” is a film resulting from atleast one thermochromic formulation that is substantially dry, ascharacterized by the residual liquid carrier medium being in the rangeof 1-5 weight % of the total weight of the film.

A “reflective formulation” is a formulation, as defined above, whichcomprises at least a polymeric resin in a liquid carrier medium, asdefined above, and further comprises at least one colorant (white ornon-white).

As used herein, a “reflective layer” is a film resulting from at leastone reflective formulation that is substantially dry, as characterizedby the residual liquid carrier medium being in the range of 1-5 weight %of the total weight of the film.

A “white reflectance layer” is one that reflects 95% of visibleelectromagnetic radiation incident upon it.

A “protective formulation” is a formulation, as defined above, whichcomprises at least a polymeric resin selected for environmental ormechanical protection of the underlying article, upon application ontosaid article.

A “protective layer” is a film resulting from at least one protectiveformulation that is substantially dry, as characterized by the residualliquid carrier medium being in the range of 1-5 weight % of the totalweight of the film.

A “stabilizing additive” is a material added to a formulation comprisingsolid particles or a dispersion to uniformly distribute, preventagglomeration, and/or prevent settling of solid materials in saiddispersion in said liquid carrier medium to result in an enhancement ofluminous intensity. Such stabilizing additives generally comprisedispersants and/or rheology modifiers.

A “preformed article” is any article onto which at least one layer maybe applied. A preformed article may be rigid or flexible.

As used herein, “visible electromagnetic radiation” is characterized byelectromagnetic radiation with wavelengths in the region of 400nanometers (“nm”) to 700 nm.

As used herein, “Film Transmissivity” (“FT”) is the fraction of incidentvisible electromagnetic radiation transmitted through a layer.

“Photolytic degradation” is deterioration, degradation, or change inproperties, such as observed color, that is initiated by electromagneticradiation.

The present invention relates to thermochromic materials that areformulated to be liquid mixtures with stabilizing additives comprisingpolymeric resin binders, dispersants, rheology modifiers, and wettingagents so as to be highly transmissive of visible electromagneticradiation in the colorless thermochromic state upon application to anyarticle.

The present invention also relates to the use of photoluminescentfluorescent pigment materials to render color or aid in rendering colorupon triggering of thermochromic materials into a colorless state.

The present invention also relates to the use of the luminescentfluorescent dye materials such that they exist as solid solutions in thepolymeric resin matrix, thereby creating high ratio of emission per unitweight of material deployed for rendering color or aid in renderingcolor upon triggering of the thermochromic materials into a colorlessstate

The present invention also relates to the use of photostabilizers eithersingly or in combination or with a combined functionality in a singlemolecule to retard the photolytic degradation of said thermochromic andphotoluminescent fluorescent materials cited above.

The present invention also relates to a thermochromic objects comprisingat least one thermochromic layer, wherein said thermochromic layer ishighly transmissive of visible electromagnetic radiation and wherein thethermochromic materials have been triggered into a colorless state.

The present invention also relates to a thermochromic objects comprisingat least one thermochromic layer, as defined above, but which mayadditionally comprise photoluminescent fluorescent pigments, dyes, orboth, as described above.

The present invention also relates to the construction of athermochromic objects comprising at least one thermochromic layer, asdefined abov,e but which may additionally comprises photostabilizers, asdescribed above

The present invention also relates to the construction of athermochromic object which comprises a thermochromic layer, as definedabove, wherein the thermochromic layer functions as an optical switch totransition from either a colored state to a colorless state or from acolorless state to a colored state.

The present invention also relates to a thermochromic object whichcomprises a reflective layer comprising polymeric resin and white orcolored pigments, wherein the reflective layer is highly reflective ofunabsorbed visible electromagnetic radiation and wherein such reflectivelayer is deployed in conjunction with a thermochromic layer.

The present invention also relates to a thermochromic objects comprisinga reflective layer, as defined above, and additionally comprisingphotoluminescent fluorescent pigments wherein the reflective layer ishighly reflective of unabsorbed visible electromagnetic radiation.

The present invention also relates to a thermochromic object comprisinga reflective layer, as defined abov,e and additionally comprisingphotoluminescent fluorescent dyes wherein the photoluminescentfluorescent dye exists as a solid solution in polymeric matrix whereinthe reflective layer is highly reflective of unabsorbed visibleelectromagnetic radiation.

The present invention also relates to a thermochromicobject comprising areflective layer as defined above which additionally comprisesphotostabilizers as defined above to retard the photolytic degradationof said thermochromic and photoluminescent fluorescent materials citedabove

When the thermochromic object according to the invention comprises atleast one reflective layer and at least one thermochromic layer, thereflective layer is applied first, so that it is proximal to thepreformed article. The thermochromic layer is applied after thereflective layer, so that said thermochromic layer is distal to saidpreformed article. If transfer technology is used, it must be used suchthat the result is the same.

The present invention also relates to a thermochromic object comprisingat least one protective layer which comprises a polymeric resin andwherein the protective layer is deployed in conjunction with anthermochromic layer and wherein the protective layer provides physicalprotection to the thermochromic layer.

The present invention also relates to a thermochromic object comprisingat least one protective layer as defined above but which additionallycomprises photostabilizers as described above.

When the thermochromic object according to the invention comprises atleast one thermochromic layer and at least one protective layer, thethermochromic layer is applied first, so that it is proximal to saidpreformed article. The protective layer is applied after thethermochromic layer, so that said protective layer is distal to saidpreformed article. If transfer technology is used, it must be used suchthat the result is the same.

When the thermochromic object according to the invention comprises atleast one reflective layer, at least one thermochromic layer, and atleast one protective layer, the reflective layer is applied first, sothat it is proximal to said preformed article. The thermochromic layeris applied next and then the protective layer is applied. Therefore, thereflective layer is proximal to the preformed article, the protectivelayer is distal to said preformed article, and said thermochromic layeris between said reflective layer and said protective layer. If transfertechnology is used, it must be used such that the result is the same.

The present invention also relates to the method of making athermochromic object with at least one thermochromic layer.

The present invention also relates to the method of making athermochromic object with at least one reflective layer and onethermochromic layer.

The present invention also relates to the method of making athermochromic object with at least one thermochromic layer and at leastone protective layer.

The present invention also relates to the method of making athermochromic object with at least one colorant layer and at least onethermochromic layer.

The present invention relates to the method of making a thermochromicobject with at least one reflective layer, at least one thermochromiclayer and at least one protective layer.

The present invention relates to the method of making a thermochromicobject with at least one colorant layer, at least one thermochromiclayer and at least one protective layer.

The present invention relates to the method of making a thermochromicobject with at least one reflective layer, at least one colorant layer,at least one thermochromic layer and at least one protective layer.

In order to produce these products, one needs to develop a systemconstruction such that the visual impact of the color change isstriking, the indicator indicia are robust, the applied images patternsor indicia are photolytically stable and the product is not only durablefor the user but also environmentally stable. One also needs to developproducts that are desirable and useful to consumers in many fields ofuse, including food products, entertainment, sports, transportation,weather protection, decorating, indoor and outdoor sanitation or acombination thereof.

New products have surprisingly been developed that address the problemsassociated with various compounds and their uses, including developingproducts which have color changing indicators based on thermochromic,fluroscent photochromic, phosphorescent photochromic compounds or acombination thereof and that are constructed from a variey of substratematerials such as PVC acrylics, urethanes polyester, nylon, etc. Thesubstrate or surface construction materials or components may be rigidor flexible.

A system construction has also been developed such that the visualimpact of the color change is striking, the indicator indicia arerobust, the applied images patterns or indicia are photolytically stableand the product is not only durable for the user but alsoenvironmentally stable. These new products are also desirable and usefulto consumers in many fields of use, including food products,entertainment, sports, transportation, weather protection, decorating,indoor and outdoor sanitation or a combination thereof. Specifically, incontemplated embodiments, a multilayer system construction or layeredmaterial has been designed so as to create a visually striking impact ofthe color change, to be durable with respect to scratches and abrasionsand to have weatherometric robustness, such as photolytic stability andatmospheric stability for the indicator indicia or images.

One contemplated embodiment comprises a three functional layer structurewith a base layer providing functionality for maximizing or thatmaximizes the desired visual impact of the color change of at least partof the layered material, a thermochromic layer providing functionalityfor triggering a state change that is, either colorless to colored, orcolored to colorless, or from one color to another, and a protectivelayer that provides functionality for handling and weatherometricrobustness for the underlying image. The protective layer can alsoprovide a visual enhancement function when desired by providing areflective component or gloss for image viewing.

The base functional layer may produce the desired functionality eitherby a single or multiple layers of material, depending on the applicationand product. The base layer may be constructed either by blending thefinal color dye or pigment before fabrication of the layered material,such as by extrusion or molding or formation of plastic, glass, paperetc., or by a coating application process such as gravure, flexo, rollor blade coating etc., or by printing application processes such asscreen printing or pad printing etc. One example of a base layerconstruction would to apply a layer containing a dye or pigment materialincluding one or more fluorescent dyes or pigments that will render abrilliant final color. In this type of application, the thermochromiclayer (applied on top of this layer) would generally function as anoptical switch going from colored to colorless. This indicator could beaccomplished by the base layer having the appropriate dye or pigment forthe desired visual impact. Another application of a base layerconstruction is where the base layer contains just a white reflectivepigment coating to maximze the color rendering of the thermochromicmaterials. In this type of application the thermochromic layer would gofrom either colorless to colored or from one color to another.

As stated earlier, the base layer may also comprise multiple layers. Anexample of a two layer base functional layer is contemplated when thebase layer is being applied to a rigid or flexible plastic or othermaterial containing a strong absorbing color different from the finalcolor. In such a case so as not to reduce final color impact orvibrancy, the base layer will consist of a hidden layer consisting of awhite reflective pigment application followed by the layer rendering thefinal color such as that described above.

There will be occasions where in order to create a visually-strikingfinal color, it may be necessary to first apply a specific contrastingcolor layer to enable striking visual impact of the final color. In suchan embodiment, the base functional layer could become a three layerconstruction. In this case, one has to first create a desired oversized(oversized relative to final color image) contrast color image followedby a white reflective image followed by final color image application.

The base layer, in addition to serving the function of enhancing thevisual impact of the final color, will also serve as a platform for theadditional layers and/or functional layers. Therefore, it is importantto consider the components of the base layer with respect to thecomponents of additional layers in order to avoid color bleeding,undesirable chemical reactions between layers of materials anddeterioration of the desired visual impact of the layered materials.

The second layer applied on top of the base layer will contain thethermochromic layer. The thermochromic layer may have one or morelayers, where the layer or layers comprise at least one layer ofenvirochromic dyes, pigments or inks. Envirochromic dyes, pigments orinks are those that change color or texture with a changing environment,such as heat, cold, rain, sunshine, UV rays, snow, dark, light or acombination thereof. Envirochromic dyes, pigments or inks arecontemplated to be those described herein earlier, conventionalenvirochromic dyes, pigments or inks, envirochromic dyes, pigments orinks that are yet to be developed or a combination thereof.Envirochromic inks, dyes and pigments may be clear until triggered,opaque until triggered or a particular color until triggered. Oncetriggered by an environmental condition, the ink, dye or pigment willchange—whether it changes from clear to opaque or colored, from opaqueto clear or colored or from colored to opaque or clear.

Dispersing Agents

High mechanical forces are necessary to incorporate solids in liquidmedia. It is customary to employ “dispersing agents” in order to reducethese dispersion forces and in order to keep the total energy input intothe system, which is necessary for deflocculating the solid particlesand thus the time of dispersion, as low as possible. These dispersingagents are surface-active substances of anionic, cationic, or neutralstructure. These substances are added in a small amount, either directlyto the solid or to the dispersion medium. Furthermore, it is known thateven after complete deflocculation of the solid agglomerates intoprimary particles, re-agglomeration occurs after the dispersion process.In such a case, the effort expended to produce a dispersion is partiallyor completely negated.

There is a multiplicity of different substances which are used nowadaysas dispersing agents for pigments and extenders. A review of theexisting patent literature is given in European Patent No. 0 318 999.See, e.g., Page 2, Lines 24-26. Apart from very simple, low molecularweight compounds such as lecithin, fatty acids, and salts thereof, andalkylphenol ethoxylates, for example, complex structures are also usedas dispersing agents. In particular, these comprise amino- andamide-functional systems, which are widely used amongst dispersingagents. In British Patent No. 2 153 804, for example, amino- andamide-functional poly- and oligocopolymers based on polyamines andpolycaprolactones are used for the dispersion of magnetic pigments.European Patent No. 0 713 894 describes the use of amino-functionalpolylactones for coatings and printing inks. Moreover, amine-functionalpolyacrylates, such as those disclosed in European Patent No. 0 311 157and in U.S. Pat. No. 3,980,602 are used for the stabilisation of organicand inorganic pigments. Amine-functional polymers based onpolyisocyanates constitute a further group. See, e.g., European PatentNos. 0 159 678 and 0 438 836.

Derivatives of phosphoric acid esters are also frequently used asdispersing agents. European Patent No. 0 417 490, see Page 2, Lines23-43, gives a summary of the use of these substances, preferably asdispersing agents or for the pretreatment of pigments. The salts ofacidic phosphoric acid esters are also described in this patent.Inorganic bases as well as mono- and diamines are listed as the basicsalt formation components.

While satisfactory stabilization of pigments or solids can be achievedwith one or more of the dispersing aids cited above, many of thesedispersing agents have an insufficient capacity for reducing theviscosity on the incorporation of pigments or of solid particles inbinder vehicles. Additionally, for manufacturing efficiency, there is aneed to minimize the thickness of the thermochromic layer together withthe necessity of reducing the amount of solvent as far as possible(e.g., high-solids formulations). All of this can lead to high viscositywith the resulting need for the application of excessive energy todisperse the pigment. This can result in significant degradation.

Examples of suitable dispersing aids that minimize agglomeration requirevery low levels of energy are cited for example an acrylicacid-acrylamide polymer such as those cited in U.S. Pat. No. 6,596,816,incorporated herein by reference for all purposes, or salts of an aminefunctional compound and an acid such as those cited in U.S. Pat. No.6,111,054, also incorporated herein by reference for all purposes.

Rheology Modifiers

“Rheology Modifiers” are those substances which generally can buildviscosity in liquid dispersion formulations, thereby retarding settlingof pigment materials while at the same time significantly loweringviscosity upon application of shear, to enhance smooth applicability ofsuch formulations onto articles. There is a widespread practice of usingmaterials such as colloidal silica or fumed silica and magnesiumaluminum silicate clays, such as bentonite, not only as thixotropicmodifiers to prevent sagging and running of luminescent formulation asit is applied to the object but also as suspending fillers, that is, forminimizing settling of dense pigment particles such as phosphorparticles. See, e.g., U.S. Pat. No. 6,207,077.

The common practice is to use organically-modified bentonites, silicas,hydrogenated castor oil, and polyamide waxes. A disadvantage of thesesubstances is that they are mostly dry solids which have to be broughtinto the form of a semi-finished product using solvents and shearforces, and incorporated into the liquid coating system under carefultemperature control. Failure to observe such temperatures results incrystallites in the finished coating system, which may lead to defectsin the coating.

The bigger disadvantage of their use in luminescent coatings such as thethermochromic layer is that they lead to turbidities and haze ratherthan transparent coatings. Moreover, handling dry pulverulent productswhich give rise to dusts in the course of processing is undesirable.

The present invention employs polymeric urea-urethanes in aprotic polarsolvents as rheology modifiers. This class of rheology modifiers can beused satisfactorily, that is without any scattering of electromagneticradiation, and without any significant build up of viscosity. Thus, thisclass serves not only as rheology modifiers but also to minimizesettling of the dense pigment particles. Examples of such urea-urethanescan be found, for example, in U.S. Pat. No. 6,617,468 and U.S. Pat. No.6,870,024, incorporated herein by reference for all purposes.

Wetting Agents

If the applied luminescent envirochromic layer does not contain “wettingagents,” also known as leveling agents, the resulting surface may not besmooth. Instead, the surface may be less structured, referred to ashaving a wavy surface or as having an orange peel-like surface. Thesesurfaces may be finely structured, with a short wave, or coarselystructured, with a long wave.

This waviness is unwanted not only because the surface is not visuallyappealing with a lowered market appeal, but more importantly, anysurface structure is likely to cause light scattering and loss ofperceived luminous intensity.

The structure depends on the nature and composition of the coatingcompositions; for example, on whether these coating compositionscomprise solvents or else are solvent-free, as in the case of powdercoating materials. In the case of powder coating materials it isabsolutely necessary to add leveling agents, since without theseleveling agents it is impossible to achieve a surface which is in anyway smooth.

Known examples of such agents are poly(meth)acrylates and polysiloxanes,which may be used as leveling promoters for coatings. In the case of thepolysiloxanes, the compounds generally comprise polydimethylsiloxanes,polymethylalkylsiloxanes, or else polyether- or polyester-modifiedpolydimethyl- or polymethylalkylsiloxanes. In the case of thepoly(meth)acrylates, preference is given to the use of polymers orcopolymers of alkyl acrylates having an alkyl radical chain length ofC₂-C₈, such as ethyl acrylate, 2-ethylhexyl acrylate, or n-butylacrylate, for example. The products used possess in some cases molecularweights of up to 100,000.

The action of all these products is based on surface activity at theliquid/gas interface: owing to a certain incompatibility with the actualbinder of the coating system, these products adopt an orientation to theinterface. This incompatibility may be increased by raising themolecular weight of these polymers. A disadvantage then, however, isthat owing to this incompatibility there can be cases wherein thescattering of electromagnetic radiation or haze of the layer becomeshigh, thereby resulting in significant reduction in luminous intensity.The present invention employs branched polymers comprising afree-radically or ionically polymerized base molecule into whichmonoethylenically unsaturated macromonomeric units have beenincorporated by copolymerization. Examples of such polymers may be foundin U.S. Pat. No. 6,710,127, incorporated herein by reference for allpurposes.

Other Additives

Other additives, such as “deaerators” and “defoamers” may be employed.Deaerators are those substances which minimize entrained air. Defoamersare those substances that allow easier dissipation of entrained air.Depending upon the materials comprising the formulation and theresultant viscosity, a significant amount of air entrainment can causescattering of electromagnetic radiation and, hence, a reduction inluminous intensity.

The following examples are offered to illustrate the present inventionand should not be construed in any way as limiting the scope of theinvention.

EXAMPLES Example 1

A formulation was made consisting of a thermochromic pigment in a binderof nitrocellulose and diluted with 2-methoxyethanol. This gave pigmentsolids of 40% of dry pigment to 60% Nitrocellulose binder. The solidswere contained in a solvent mixture at 45% solids. This material wascoated over plasticized PVC to give a dry coating thickness of 18microns using a screen printing process. The color of the thermochromicpigment at room temperature was selected so that it contrasted the colorof the PVC. The opacity of the thermochromic layer at room temperaturemasked the PVC layer below it. The thermochromic layer becametranslucent when heated through normal body contact to reveal thecontrasting base color of the PVC underneath.

Example 2

A formulation was made consisting of 52% thermochromic pigment in 48%Nitrocellulose binder. The pigment and binder were prepared in a solventmixture containing Toluene, Hexane, and Hydrocarbon solvents at a solidscontent of 40%. This material was applied using a silk screen to give adry coating thickness of 22 microns.

Example 3

A yellow fluorescent pigment was dispersed in 2-methoxyethanol at 50%solids using the wetting agent TegoWet 550. This dispersion was added toan acrylic binder (NeoCryl B-735) to give solids of 20% in2-methoxyethanol. The ink was then applied to plasticized PVC using ascreen print to achieve a 15 micron thickness, which provided for animage that contrasted the base color of the PVC. Over this was appliedthe formulation from Example 2 at a thickness of 26 microns. The colorof the thermochromic layer at room temperature contrasted with thefluorescent layer below it. In this case, the thermochromic layer wasdark blue compared to the fluorescent yellow of the layer below thethermochromic layer. The opacity of the thermochromic layer masked thefluorescent layer below it. The image was such that when warmed, thethermochromic pigment became translucent and revealed the fluorescentlayer printed underneath.

Example 4

Thermochromic pigment was mixed with 10% 2-methoxyethanol and thendispersed in plastisol to give a pigment concentration of 40% in thefinal mixture. This was then applied over a polyester fabric using aapplicator to give a 1 mil ending thickness.

1. A thermochromic formulation comprising: (a) an effective amount ofthermochromic materials; (b) at least one liquid carrier medium; (c) atleast one polymeric resin; and (d) at least one stabilizing additive,wherein said thermochromic materials are uniformly distributed withinsaid formulation.
 2. A thermochromic formulation comprising: (a) aneffective amount of thermochromic materials; (b) at least one liquidcarrier medium; (c) at least one polymeric resin; and (d) at least onestabilizing additive, wherein said thermochromic materials are uniformlydistributed within said formulation and further wherein said formulationhas an FT of at least 90%.
 3. The thermochromic formulation of claim 1or claim 2, which further comprises electromagnetic radiation absorptivepigment materials.
 4. The thermochromic formulation of claim 1 or claim2, which further comprises photoluminescent fluorescent pigmentmaterials.
 5. The thermochromic formulation of claim 4, wherein saidphotoluminescent fluorescent pigment materials are selected such thatthey are in solution in said liquid carrier medium and wherein uponapplication of said theromochromic layer said photoluminescentfluorescent pigment materials exist as a solid state solution saidpolymeric resin matrix.
 6. The photoluminescent formulation of any oneof claims 3-5, which further comprises photostabilizers.
 7. Thephotoluminescent formulation of any one of claims 1-6, wherein saidthermochromic materials are negative thermochromic materials.
 8. Thephotoluminescent formulation of any one of claims 1-6, wherein saidthermochromic materials are positive thermochromic materials.
 9. Thephotoluminescent formulation of any one of claims 1-6, wherein saidthermochromic materials are neutral thermochromic materials.
 10. Thephotoluminescent formulation of claim 7 or claim 8, wherein saidthermochromic materials comprise an electron donating compound and anelectron accepting compound.
 11. The photoluminescent formulation ofclaim 7 or claim 8, wherein said thermochromic materials comprise liquidcrystal materials.
 12. The thermochromic formulation of any one ofclaims 1-6, wherein said polymeric resin is selected from the groupconsisting of acrylates, poly vinyl chloride, polyurethanes,polycarbonates, polyesters, and combinations thereof.
 13. Athermochromic object comprising: (a) a preformed article; and (b) atleast one thermochromic layer wherein said thermochromic layer resultsfrom a formluation of any of claims 1-12.
 14. A thermochromic objectcomprising: (a) a preformed article; (b) at least one thermochromiclayer; and (c) at least one reflective layer; wherein said thermochromiclayer results from a formluation of any of claims 1-12, wherein saidreflective layer results from a reflective formulation, wherein saidreflective layer is proximal to said preformed article, and wherein saidthermochromic layer is distal to said preformed article.
 15. Athermochromic object comprising: (a) a preformed article; (b) at leastone thermochromic layer; (c) at least one reflective layer; and (d) atleast one protective layer; wherein said thermochromic layer resultsfrom a formulation of any of claims 1-12, wherein said reflective layerresults from a reflective formulation, wherein said protective layerresults from a protective formulation, wherein said reflective layer isproximal to said preformed article, wherein said protective layer isdistal to said preformed article, and wherein said thermochromic layeris between said reflective layer and said protective layer.
 16. Athermochromic object comprising: (a) a preformed article; (b) at leastone thermochromic layer; and (c) at least one protective layer; whereinsaid thermochromic layer results from a formluation of any of claims1-12, wherein said protective layer results from a protectiveformulation, wherein said thermochromic layer is proximal to saidpreformed article, and wherein said protective layer is distal to saidpreformed article.
 17. A method for creating a thermochromic object,said method comprising the steps of: (a) obtaining a preformed article;and (b) applying to said preformed article at least one thermochromiclayer wherein said thermochromic layer results from a formulation of anyone of claims 1-12.
 18. A method for creating a thermochromic object,said method comprising the steps of: (a) obtaining a preformed article;(b) applying to said preformed article at least one thermochromic layer;and (c) applying to said preformed article at least one reflectivelayer; wherein said thermochromic layer results from a formluation ofany of claims 1-12, wherein said reflective layer results from areflective formulation, wherein said reflective layer is proximal tosaid preformed article, and wherein said thermochromic layer is distalto said preformed article.
 19. A method for creating a thermochromicobject, said method comprising the steps of: (a) obtaining a preformedarticle; (b) applying to said preformed article at least onethermochromic layer; (c) applying to said preformed article at least onereflective layer; and (d) applying to said preformed article at leastone protective layer; wherein said thermochromic layer results from aformulation of any of claims 1-12, wherein said reflective layer resultsfrom a reflective formulation, wherein said protective layer resultsfrom a protective formulation, wherein said reflective layer is proximalto said preformed article, wherein said protective layer is distal tosaid preformed article, and wherein said thermochromic layer is betweensaid reflective layer and said protective layer.
 20. A method forcreating a thermochromic object, said method comprising the steps of:(a) obtaining a preformed article; (b) applying to said preformedarticle at least one thermochromic layer; and (c) applying to saidpreformed article at least one protective layer; wherein saidthermochromic layer results from a formulation of any of claims 1-12,wherein said protective layer results from a protective formulation,wherein said thermochromic layer is proximal to said preformed article,and wherein said protective layer is distal to said preformed article.